This invention relates generally to the field of hard disc drive data storage devices, and more particularly, but not by way of limitation, to magnetic latches for holding disc drive actuators in their park position.
Disc drives of the type known as xe2x80x9cWinchesterxe2x80x9d disc drives, or hard disc drives, are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 15,000 RPM.
Data are recorded to and retrieved from the discs by an array of vertically aligned read/write head assemblies, or heads, which are controllably moved from track to track by an actuator assembly. The read/write head assemblies typically consist of an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative hydrodynamic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by flexures attached to the actuator.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. An actuator bearing housing is mounted to the pivot shaft by an arrangement of precision ball bearing assemblies, and supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member. These magnets are typically mounted to plates, also known as pole pieces or simply poles, which are mounted in positions vertically spaced from one another.
On the side of the actuator bearing housing opposite to the coil, the actuator assembly typically includes a plurality of vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. These actuator arms extend between the discs, where they support the head assemblies at their desired positions adjacent the disc surfaces. The drive further includes a voice coil motor (VCM) which operates in the following manner. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator bearing housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator bearing housing rotates, the heads are moved generally radially across the data tracks of the discs along an arcuate path.
When power to the disc drive is lost or when the disc drive is not in operation, some method for restraining the rotation of the actuator arms must be used so as to avoid damage to the disc surfaces or to the heads. One known restraint method is to move the heads to a parking zone and to latch the actuator in that position until power is restored to the disc drive. This parking zone is typically located at an inner diameter of the disc or just outside the outer diameter of the disc. In the latter case, the head may be moved off of and onto the disc by means of a ramp.
One conventional latching system involves a first, magnetically permeable latch member that is fixed relative to the base of the disc drive housing and a second, magnetically permeable latch member that is attached to the yoke of the actuator. The second latch member is thus capable of traveling in a substantially horizontal arcuate path about the pivot shaft. The first latch member is generally vertical and located near the permanent magnet of the voice coil magnet assembly so that it is capable of holding the second latch member by magnetic attraction when the disc drive is not in operation. The first latch member also forms part of the VCM magnet assembly in that it is fixed between the upper and lower poles of the VCM. The permanent magnet is usually connected to the lower pole which is in turn mounted to the base of the disc drive housing.
The conventional method of assembling the first latch member involves first mounting the lower plate to the base of the disc drive housing. The lower plate includes a hole into which an end portion of the first latch member is inserted. After mounting the actuator to the base of the disc drive housing, the upper pole is installed. The upper pole also includes a hole which serves to locate the upper end of the first latch member and to secure it in place.
There are many problems associated with this conventional magnetic latch structure. One problem is that an extra part is required, namely the first latch member. This additional part is costly. Moreover, installation of this latch requires a number of assembly steps. Tolerances between the latch and the poles must be must be very close in order to accurately park the actuator, requiring precise manufacturing and assembly methods. All of these factors require additional time and expense.
What the prior art has been lacking is a latch structure which is simple in construction, inexpensive and easily manufactured and assembled while still providing precise positioning of a parked actuator.
Disclosed is a magnetic latch assembly. In a preferred embodiment, upper and lower poles are each provided with protruding portions which bend to extend vertically toward each other. The two bent portions together form a vertical magnetic latch member configured to attract a magnetically permeable element located on an actuator. Each bent portion may have a locating feature for accurately positioning the bent portions relative to one another.
Additional features and benefits will become apparent upon a review of the attached figures and the accompanying description.